Group III-nitrides such as gallium-nitride and alloys thereof are becoming popular in the manufacturing of optical devices as well of power devices.
Group III-nitride based devices are predominantly formed on a sapphire substrate as the lattice mismatch between the sapphire substrate and the group III-nitride layers is minimal.
In order to reduce the overall manufacturing cost, there is tendency to grow the group III-nitride layers on a silicon substrate. This approach is commonly known as gallium nitride-on-silicon (GaN-on-Si). An advantage of this GaN-on-Si approach is that it allows manufacturing of such group-III nitride based devices on established silicon manufacturing equipment resulting in a reduced manufacturing cost.
However, due to strain created by the lattice mismatch between the group-III nitride layers and the silicon substrate, bowing and cracking of the GaN-on-Si wafers is a concern. Moreover, as the silicon substrate is opaque, this silicon substrate needs to be removed in case the group-III nitride based device is intended for optical applications.
Hence, there is a need for method for forming group III-nitride based devices which method offers an improved immunity towards strain induced in the group III-nitride based device.